import express from "express";
import { randomUUID } from "node:crypto";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
import { registerCoreTools } from "./tools.js";
function createServerInstance() {
const server = new McpServer(
{ name: "mcp-mold-server", version: "0.1.0" },
{
capabilities: { resources: {}, tools: {}, prompts: {} },
debug: true,
logLevel: "verbose",
}
);
registerCoreTools(server);
return server;
}
export async function startStreamableHttp({ port } = {}) {
const httpPort = Number(
port ?? process.env.MCP_HTTP_PORT ?? process.env.MOLD_HTTP_PORT ?? 3000
);
const app = express();
app.use(express.json());
const transports = /** @type {Record<string, StreamableHTTPServerTransport>} */ ({});
app.post("/mcp", async (req, res) => {
const sessionId = req.headers["mcp-session-id"]; // header name is case-insensitive in Node
let transport;
if (sessionId && transports[sessionId]) {
transport = transports[sessionId];
} else if (!sessionId && isInitializeRequest(req.body)) {
transport = new StreamableHTTPServerTransport({
sessionIdGenerator: () => randomUUID(),
onsessioninitialized: (sid) => {
transports[sid] = transport;
},
// Consider enabling DNS rebinding protection for local deployments:
// enableDnsRebindingProtection: true,
// allowedHosts: ["127.0.0.1"],
});
transport.onclose = () => {
if (transport.sessionId) delete transports[transport.sessionId];
};
const server = createServerInstance();
await server.connect(transport);
} else {
res.status(400).json({
jsonrpc: "2.0",
error: { code: -32000, message: "Bad Request: No valid session ID provided" },
id: null,
});
return;
}
await transport.handleRequest(req, res, req.body);
});
const handleSessionRequest = async (req, res) => {
const sessionId = req.headers["mcp-session-id"];
if (!sessionId || !transports[sessionId]) {
res.status(400).send("Invalid or missing session ID");
return;
}
const transport = transports[sessionId];
await transport.handleRequest(req, res);
};
app.get("/mcp", handleSessionRequest);
app.delete("/mcp", handleSessionRequest);
await new Promise((resolve, reject) => {
const server = app.listen(httpPort, (err) => {
if (err) reject(err);
else resolve();
});
server.on("error", reject);
});
console.error(`[mcp-mold] Streamable HTTP listening on :${httpPort}`);
}
